The use of fiber optic technology in the communications industry continues to increase. As is known in the art, fiber optic communications provide numerous advantages such as increased bandwidth, less noise, lower signal-to-noise ratio requirements, and lower error rates. In addition, the use of fiber optic cable relative to metallic conductors permits more communication across the same space previously required by metallic conductors.
As known in the art, communication of signals through an optic fiber is accomplished by placing communications circuitry at the tips of both ends of the optic fiber. For purposes of this document, such communications circuitry includes "photonic devices", that is, devices for conversion of signals between electrical and optical media. FIG. 1A illustrates a perspective view of certain components of such a system. Specifically, FIG. 1A illustrates a carrier 10 which is commonly disposed within a fiber optics package (shown in FIG. 1B). As known in the art, carrier 10 supports a laser 12. Although not shown, it is also known in the art that carrier 10 typically supports various components such as a thermistor, a back-wave detector, and may also support a subcarrier and/or a submount to support laser 12.
Carrier 10 further includes an integral extension 14 which supports an adjustment post 16. A small mass of solder (not shown) supports a fiber retaining slab 18 on top of adjustment post 16. Slab 18 includes a longitudinal groove 20 on the order of 0.01 inches in width. An optic fiber 22 extends from a sleeve 24 and is retained within groove 20. The tip 26 of fiber 22 extends inwardly beyond the edge of slab 18 and immediately proximate laser 12. Thus, laser 12 can communicate signals to fiber 22 by transmitting signals to tip 24 of the fiber.
FIG. 1B illustrates a perspective and cutaway view of carrier 10 when disposed within a prior art fiber optics package 28. Package 28 is typically a parallelepiped in shape having a length on the order of 1.0 inch and a width and height on the order of 0.75 inches. Package 28 is carefully constructed to hermetically house various components, including carrier 10. A ferrule 30 permits access through a hole or "pass through" in one side of package 28. Sleeve 24 passes through ferrule 30, thereby permitting optic fiber 22 to extend into the interior of package 28. Typically, solder 32 or an alternative sealant is used at the interface between sleeve 24 and ferrule 30 so that contaminants may not pass via this interface into the interior of package 28. A thermal electric cooler 34 supports carrier 10 and its associated componentry. In addition, package 28 houses an integrated circuit 36 which connects in various manners to the componentry of carrier 10, and also to a series of package pins 38. A pair of power conductors 40 are connected to respective power pins 42. Thus, signal interaction to the communications circuitry and power supply to thermal electric cooler 34 may be accomplished external from package 28 by accessing pins 38 and 42.
Having illustrated a prior art carrier 10 and its use, note the critical importance in aligning fiber tip 26 with respect to laser 12. In the prior art embodiment of FIG. 1A-B, optic fiber 22 is commonly affixed within retaining slab 18 by use of solder (for a metalized fiber) or epoxies (typically, for a non-metalized fiber). Specifically, either of these materials are used to form deposits 44 and 46 along slab 18 to retain fiber 22 along groove 20. While performing their respective retention function, each of these materials provides various drawbacks and potential problems in connection with the overall system. For example, as is known in the art, solder tends to move or creep over time due to stress. As another example, solder creates a known ratcheting effect due to fluctuations in temperature. Thus, both the solder used as deposits 44 and 46 as well as the solder between post 16 and slab 18 may tend to change position over the life-span of the system. Such a change correspondingly moves the otherwise fixed position of tip 26 of optic fiber 22. As is known in the art, tolerances for movement of tip 26 are typically only on the order of 0.1 microns. Naturally, therefore, excessive movement of tip 26 is unacceptable and may reduce or eliminate the ability of the system to communicate along optic fiber 22. Conductive epoxy and like materials also suffer due to their corrosive and/or contaminating effects. In addition, quite often these materials produce gaseous byproducts which may interfere with the sensitive operation of laser 12. Thus, these materials also present a risk to the long term reliability of the system of FIGS. 1A-1B.
One solution for addressing the above is disclosed in pending U.S. application Ser. No. 07/990,899, U.S. Pat. Ser. No. 5,301,251 entitled "METHOD AND APPARATUS FOR AFFIXING AN OPTIC FIBER TIP IN POSITION WITH RESPECT TO A FIBER COMMUNICATIONS CIRCUIT", having inventors Andrew Moore, David Ma, Harry Bohnam, and Robert Bontz, and which is hereby incorporated herein by reference. FIGS. 2A and 2B of the present document illustrate simplified figures of FIGS. 3C and 3B, respectively, of the figures in the above-incorporated application, and introduce one concept of that application.
In the present document, FIG. 2A illustrates a perspective view of a carrier 48 shown which is similar in some respects to carrier 10 shown in FIGS. 1A-B, above. In general, carrier 48 supports the same communications circuitry as carrier 10 and, again, for purposes of ease of illustration, only a laser 50 is shown (with it understood that other items may be supported, such as a thermistor, a back wave detector, a sub-carrier, and a sub-mount). While FIG. 2A illustrates a transmitter (i.e., laser 50), it should be understood that a receiving device, such as a photodiode, could be included as an alternative. Moreover, the circuitry for communicating to/from the fiber could be a transceiving device as well.
Carrier 48 is generally parallelepiped in shape having sides 52 and 54, and ends 56 and 58. Carrier 48 is on the order of 0.4 inches in length, and 0.25 inches in width, and 0.1 inches in thickness. Note that unlike carrier 10 of FIGS. 1A and 1B, carrier 48 does not include an integral extension 14 to support a post 16 and a retaining slab 18. In contrast, and shown separately in FIG. 2B, a separate and independent block 60 is placed adjacent end 58 of carrier 48. Block 60 supports a positioning member 62 which positions fiber 22 within block 60, and also affixes fiber tip 26 in place with respect to laser 50.
In FIG. 2B, positioning member 62 is disposed within channel 64 of block 60. At this point, optic fiber 22 is freely moveable in an axial direction with respect to positioning member 62. Given these components, eventually, optic fiber 22 is fixed within block 60 and block 60 is fixed with respect to carrier 48. Thus, one skilled in the art will recognize that the positioning of fiber tip 26 with respect to laser 50 is determined in three dimensions: (1) one dimension defined as the fiber tip is moved axially toward or away with respect to laser 50; (2) one dimension as block 60 moves horizontally with respect to carrier 48; and (3) one dimension as block 60 moves vertically with respect to carrier 48.
Given the above, and further in view of the precise tolerances of fiber tip 26, one skilled in the art will appreciate the precision required in moving fiber 22 axially, as well as adjusting block 60 with respect to carrier 48 prior to affixing the components together. One approach to such adjustments is a manual adjustment in each of the above three recited dimensions. Such an approach however suffers numerous drawbacks. For example, human error is introduced into the adjustment process. Second, such a process is timely and, therefore, increases cost and lowers supply. Still other disadvantages are readily apparent to one skilled in the art.
It is therefore an object of the present invention to provide an improved method and apparatus for aligning a separately supported fiber tip and fiber communications circuit.
It is a further object of the present invention to provide such a method and apparatus for quickly and efficiently aligning a fiber tip and fiber communications circuit.
It is a further object of the present invention to provide such a method and apparatus for aligning a fiber tip and fiber communications circuit in an automated fashion to reduce or substantially eliminate human error otherwise existing in the alignment process.
It is a further object of the present invention to provide such a method and apparatus for reducing the possibility of subsequent movement of an optic fiber tip with respect to its associated communications circuit.
It is a further object of the present invention to provide such a method and apparatus for providing improved axial and radial adjustment of the tip of an optic fiber with respect to its associated communications circuit.
Still other objects and advantages of the present invention will become apparent to those of ordinary skill in the art having reference to the following specification together with its drawings.